Certain microorganisms can produce fuels, such as ethanol, and other chemicals, such as 2,3-butanediol, by fermentation of gaseous substrates comprising one or more of carbon monoxide (CO), carbon dioxide (CO2), and hydrogen (H2). However, efficient production of such fuels and chemicals may be limited diversion of carbon substrates into undesired byproducts or by slow microorganism growth. Accordingly, there remains a need for genetically engineered microorganisms having improved product and/or growth profiles.